Ancient baleen whales were predators not filter feeders
Recent research reveals ancient baleen whales had different teeth to today’s filter feeding morphology.
Baleen whales, otherwise known as mysticetes, include the humpback whale, blue whale and fin whale, among many others. Modern mysticetes are some of the largest mammals hat have ever lived, but unlike other mammals, they have no teeth. Their name arises from their bristle-like structures known as baleen that allows them to filter krill from the ocean. The other major group of cetaceans are known as toothed whales or odontocetes, which include orca, sperm whales, dolphin and porpoise species.
Teeth are usually the main adaptation used during feeding and their shape can indicate how and what an animal eats. For example, predators require sharp teeth to both kill and chew their prey. It has long been thought that the teeth of prehistoric baleen whales were shaped much like modern leopard and crab eater seals being blunt, rounded with open inter cusp notches used for filter feeding krill, which then eventually led to the evolution of baleen and bulk filter feeding.
A new species of ancient whale Coronodon havensteini was recently discovered. The back molars were large and the spaces between the whale’s teeth were large as well. It was thought that the species relied on the species between their large teeth for filtering. However, this theory has never been tested. In order to investigate whether ancient baleen whales have always been filter feeders or whether they once were predators, 3D models of the teeth of eight extinct whale species were compared to four terrestrial carnivores and five seal species that were capable of capturing and processing prey. Two of the seal species included the filter feeding leopard and crabeater seals.
The results revealed that ancient baleen whales had sharp teeth more similar to those of terrestrial carnivores than the filter feeding seals indicating that their function was once used for piercing and cutting prey rather than filtering. None of the extinct cetaceans had the blunt, rounded teeth specialised for filtering seen in the extant leopard seal and crab eater seal.
While the recent discovery appears to have solved some hypotheses, it also raises questions as to how modern mysticetes evolved baleen. The new research indicates that in the past they had teeth before they then evolved into suction feeders. Suction feeding is used by many marine mammals today whereby large volumes of water and fish are pulled into the mouth. As the whales became suction-feeding specialists, their teeth began reducing in size before eventually being lost and baleen then evolving. More research is required in order to fully understand the origins of today’s baleen whales, but this is a great start.
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